Avoid flashing or flickering content


Rule ID: flickering

For people who have epilepsy or other photosensitive seizure conditions, flashing material on a website can be problematic. These users might experience a seizure in response to flashing content.

This rule gives only a hint and requires manual verification.


According to WCAG 2.1, Success Criterion 2.3.1, items on a web page cannot flash more than three times in a single second or less frequently than the general and red flash thresholds. Its goal is to make the experience accessible for people who could be photosensitive or have seizures.

How to fix it


If the flashing content is below a specific size (that’s dependent on the viewport), it passes the criterion regardless of the flash threshold.


Accessibility, WCAG 2.1, Success Criterion 2.3.1 Three Flashes or Below Threshold, Level A